1. Field of Invention
The present invention relates to a circuit substrate and a manufacturing method thereof, and more generally to a circuit substrate and a manufacturing method thereof for enhancing the process performance.
2. Description of Related Art
Currently, a method of fabricating a circuit substrate with fine patterns and high density uses a semi-additive process (SAP) to form a required circuit layer. Semi-additive processes are divided into two groups: Ajinomoto build-up film (ABF) semi-additive process and non-ABF semi-additive process, depending on the characteristics of insulating materials.
A conductive layer can be directly fabricated on an ABF after the surface of the ABF is roughened. Semi-additive steps such as lithography, plating, stripping and etching steps are then performed, so as to form a circuit layer with fine patterns. The production cost is high because the insulating material is limited to be an ABF.
The manufacturing method using a non-ABF includes pressing a thin copper layer on the surface of the non-ABF. Semi-additive steps such as lithography, plating, stripping and etching steps are then performed, so as to form a circuit layer with detailed. The process performance of the method using a non-ABF is lower than that of the method using an ABF because the thin copper layer has poor adhesion to the non-ABF. Accordingly, in the current semi-additive process, when a specific material such as an ABF is used, a plating copper can be formed on the ABF without forming a bottom copper before forming the plating copper. On the other hand, when a non-ABF is used, both bottom copper and plating copper are required to form on the non-ABF.